Prior art patent document published EP 2 791 409 A1 discloses a gas cylinder tap with a pressure reducer and a flow selector. The flow selector is operated by means of a hand-wheel that rotates a disk with calibrated holes arranged along a circle in order to bring a specific hole of a calibrated section in front of a gas passage fluidly connected to the gas outlet of the tap. A pressure indicator is housed in the hand-wheel and is mounted on the tap so as not to rotate with the wheel. Indeed, the pressure indicator is supported by a thin shaft that extends through a larger shaft of the hand-wheel and also through the piston of the pressure reducer. The piston comprises a closure element that cooperates with a seat in the tap body. The thin shaft holding the pressure indicator extends through the piston until the closure element so as to be constantly in fluidic connection with the high pressure directly upstream of the seat. The pressure indicator provides therefore information of the pressure in the gas cylinder. This arrangement is however rather bulky in the longitudinal direction of the tap. Also, the pressure indicator is mechanically linked to the piston of the pressure reducer. This means that the pressure indicator is likely to disturb the functioning of the pressure reducer. Indeed, the frictional forces between the shaft and the guiding surfaces in the shaft of the hand-wheel will interfere with the forces acting on the piston for the regulation of the pressure. In addition, the presence of dust or particles between the pressure indicator housing and the internal surface of the hand-wheel might even increase that negative interference.
Prior art patent document published U.S. Pat. No. 6,283,146 B1 discloses also a gas cylinder tap with a pressure reducer and a pressure indicator housed in a hand-wheel. Similarly to the above discussed teaching, the pressure indicator does not turn together with the hand-wheel. This tap does not however comprise any flow selector. The hand-wheel adjusts the pre-setting of the pressure reducer. The pressure indicator is held by a sophisticated arrangement comprising a pressure gauge guide that is longitudinally held in place by means of bolts screwed in a rotatable sleeve of the hand-wheel and engaging in a groove of the guide. This latter is engaged with a non-rotating spring retainer of the pressure reducer, and this in a sliding but non-rotating manner. The pressure indicator is in fluidic connection with the reduced pressure, contrary to the previous document where the pressure indicator is connected to the high pressure in the inlet.